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However, it said 30,000 people who had a private pension never reported their Department of Social Welfare pension to Revenue.

Some 85,000 individuals under-reported their circumstances or their situation had changed since they had originally contacted Revenue.

The organisation refunded €1.1m to pensioners who paid too much tax.

In its annual report today, Revenue admitted its approach "did upset some people."

On the property tax, Revenue said because it had drawn up a list of homeowners from multiple sources there had been errors which it had anticipated and had tried to explain.

It said when it started preparing to collect the tax there was neither a complete register of residential properties nor a system of valuing homes in place.

In its annual report, it said this represented a "huge challenge".

Revenue said the tax was easy to pay but difficult to avoid.

One million litres of illegally laundered fuel was seized, while nearly 100 million illegal cigarettes valued at €45m were also seized.

The authority's annual report said that the cost of running Revenue fell by €10.4m last year. Since 2008, annual running costs were reduced by over €103m (21%).

Speaking at the launch of the report, the Chairman of the Revenue Commissioners, Josephine Feehily, said that debt available for collection was just under €1.2 billion, down 10.4% from 2011.

''The continuing trend in decreasing levels of debt available for collection in the last couple of years is very encouraging,'' she said.

Revenue has sent out over 1.6 million property tax letters

Ms Feehily said she was ''pleased'' to report that Revenue had reached its target of issuing letters in respect of over 1.6 million properties for local property tax.

However, she admitted that not everyone who was liable to pay had received a letter. She estimated the numbers who failed to get a letter was "in the thousands".

But she stressed people who were liable and who had not received a letter had to contact Revenue and pay the tax.

She noted that the first LPT receipts have been credited to the Exchequer and, with over five weeks to go to the online filing deadline, more than 218,000 property tax returns have been received by Revenue.

Revenue will begin deducting estimates of property tax from payroll or social welfare payments of people who have refused to pay the charge at the end of June.

Self assessed tax payers who have not paid the property levy will be surcharged on their tax return from the October. That will have the effect of doubling the charge.

Ms Feehily described the reaction from the public to the tax as ''excellent''.